There are monitors that natively support SOG (sync-on-green), and others that don't, the others that don't support it, they need some extra components to separate the video sync from the green channel, and that can be done with a LM1881 chip in order to make it work. Do this at your own risk, I'm not responsible for what might happen to your hardware, make sure you do everything with caution, you follow up the instructions correctly and carefully and you always analyze voltage and amperage endings to make sure what you are doing is meeting your hardware specifications.This mod worked for me, but it doesn't mean that it might end up working the same way for you, i just tested it with my Playstation 2, always making sure that nothing will blow up. But be aware that every hardware has its own specifications and limitations, also every Playstation 2 has its own specifications and limitations, so If you are not an expert, and you don't know what you are doing, don't try to attempt this. Board project: i added a diode (don't invert the polarization otherwise this will not work) between the Playstation 2 Green and the VGA green pins, this way i can remove the synchronization from green. But since the diode has an internal resistance, this makes the green wave signal weak, so i added a potentiometer connected to GND and VCC that allows me increase the wave before it gets rid of the sync signal.In short the potentiometer amplifies the wave, then the diode removes the sync and reduces the wave to it's correct shape.
Playstation 2 Board Pure Rgb Sync System
This is not a perfect solution and you'll still be able to see some remaining green (almost none) in some particular areas, that you can compensate or remove with the potentiometer. If your game is almost of the same colors, then you just leave the potentiometer as it is, and you keep playing. If you feel like you want to make it work even better, you can use an Arduino to analyze the voltage (like your multimeter is already doing), and increase or decrease the voltage sending an PWM signal like your potentiometer is doing, this way you have an automatic process that increases or decreases the green when you need it.
A composite sync or CSYNC RGB SCART supplies a clean timing signal without composite video interlaced on the same wire, as seen in figure 2 which gives a clearer picture in some cases. Composite sync is also sometimes referred to as 'pure sync', “clean sync” or 'CSYNC'. Pinout of PlayStation 2 / 3 Special DSUB VGA CableComponent to VGA RGB PlayStation 2 /3 Cable (no sound) Pinouts / Devices / Connectors. Videogames connector or cable. PlayStation 2 / 3 Special DSUB VGA Cable pinout. This cable works ONLY with Sync-on-Green monitors! How to access run. If your monitor dosn't support Sync-on-Green you need additional.
Sega Mega Drive and SNK Neo Geo AES RGB AV Scart TV cable leads.